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among traits in seedlings were similar to those observed in older field-grown trees, indicating that
these traits are controlled by similar sets of genes in the two age classes. Nursery-field
correlations between comparable traits were consistent across nursery regimes, but rxy was strong
enough to be useful for early testing purposes (i.e. | rxy | 0.30), only for number of
whorls with steep-angled branches (WSAB), branch length, and branch angle in older trees.
Predicted gains from early selection for these or correlated traits were at least 40-50% of those
expected from selection at older ages. Because of unfavourable genetic correlations, selection for
stem growth potential alone at the seedling stage is expected to produce unfavourable impacts on
WSAB and stem sinuosity in older trees. To avoid such negative effects on wood quality, both
stem form and branching traits should be included as selection criteria in Douglas fir breeding
programmes.
633. Velazquez-Martinez, A. and D.A. Perry. 1997. Factors influencing the availability of nitrogen in
thinned and unthinned Douglas-fir stands in the central Oregon Cascades. Forest-Ecology-and-
Management 93(3): 195-203.
Keywords: fertilization
thinning
soil properties
Abstract: Soil N mineralized during 7-day anaerobic incubation at 40 degrees C (available
N) was compared at 2 soil depths and correlated with soil and site factors in Douglas fir
[Pseudotsuga menziesii] stands with different combinations of thinning and multinutrient
fertilizing. Available N expressed either on an area basis (kg ha-1) or on a concentration basis
(mg kg-1) at the 2 depths did not vary significantly by stocking density, treatment, or densitytreatment
interaction. There was a significant difference between the soil depths, averaging 39 mg
kg-1 at 0-20 cm depth, and 20 mg kg-1 at 20-40 cm depth. Available N was positively correlated
with total soil N, exchangeable Ca, and adjusted aspect (the former 2 factors accounting for 46%
of the total variation), and negatively with rock content and slope steepness. Stand density had no
effect.
634. Velazquez-Martinez, A., D.A. Perry and T.E. Bell. 1992. Response of aboveground biomass
increment, growth efficiency, and foliar nutrients to thinning, fertilization, and pruning in young
Douglas-fir plantations in the central Oregon Cascades. Canadian-Journal-of-Forest-Research
22(9): 1278-1289.
Keywords: fertilization
thinning
pruning
growth
carbon allocation
tree physiology
tree morphology
Abstract: The effect of thinning and silvicultural practices (multinutrient fertilization
and/or pruning) on total aboveground biomass increment and growth efficiency was studied over
three consecutive 2-year periods (1981-1987) in young Douglas fir (Pseudotsuga menziesii)
plantations in the central Oregon Cascades. Plantations were 21-27 yr old in 1987. Plots were
heavily thinned (leaving 300 trees/ha), moderately thinned (leaving 604 trees/ha) or left
unthinned (leaving 3459 trees/ha) in 1981. Fertilizer (N, P, K, Ca, S and Fe) was applied with
slow-release tabs. Net above-ground biomass annual increment over the 6-year period averaged